Repairs and inspections performed within the reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically are performed with ropes and poles for manual manipulation of simple tools or manual delivery of dedicated automated tools. More specifically, the RPV typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide typically is spaced above a core plate within the RPV. Many other components, e.g., steam dryers, also are located in the RPV.
During reactor shut down, and if it is desired to inspect or repair certain components within the RPV, the RPV top head is removed. Other components such as the steam dryers may also be removed to enable access to RPV locations between the top guide and core plate or locations below the core plate. To perform the inspections and repairs, an operator typically stands on a bridge positioned over the RPV and using ropes and poles, which may extend more than thirty (30) feet below the bridge into the RPV, inspect or repair certain RPV components. The ability to perform such inspections and repairs greatly depends on the dexterity of the operator.
In addition, it is extremely difficult to precisely position a tool within the RPV using ropes and poles. Even if the tool is accurately positioned for one operation in a desired location, it is extremely difficult to then precisely position another tool at the exact same location to perform a next step in the operation. Also, each inspection and repair operation typically requires the design and fabrication of special, dedicated tools. Designing and fabricating tools for each task is costly.
Due to the difficulty in even accessing certain locations within the RPV, performing repairs and inspections at such locations can be time consuming. It is desirable, of course, to limit the time required to perform repairs and inspections in the RPV since the reactor must be shut down to perform such tasks. Reducing the amount of time required to perform such inspections and repairs also would facilitate reducing the operator radiation exposure per task.